Continuous method of washing soap



.July 31, 1951 R. v. OWEN CONTINUOUS METHOD OF WASHING SOAPS Filed Jan. 18, 1947 4 Sheets-Sheet l INVENTOR.

Hi5 ATTORNEYS.

RONALD VINCENT OWEN Filed Jan. 18, 1947 y 1951 R. v. OWEN 2,562,207

cou'rmuous' METHOD OF WASHING SOAPS 4 Sheets-Sheet 2 INVENTOR. RONALD V/NC'N T OWEN HIS ATTORNEYS.- r

31, 1951 R. v. OWEN coNTINUous METHOD OF WASHING SOAPS 4 sheets-sheet :5

Filed Jan. 18, 1947 JNVENTORQ RONALD WNCENT OWEN Hi5 ATTORNEYS.

July 31, 1951 R. v. OWEN 2,562,207

CONTINUOUS METHOD OF WASHING- SOAPS Filed Jan. 18, 1947 Y 4 sheets sheet 4 1 INVENTOR. RONALD VINCENT OWEN MLWQ /Qd,

H15 AT TORNE Y5.

Patented July 31, 1951 2,562,207 CONTINUOUS METHOD OF WASHING SOAP Ronald Vincent Owen, Sale, England, assignor to Lever Brothers Company, Cambridge, Mass., a

corporation of Maine Application January 18, 1947, Serial No. 722,793 In Great Britain January 21, 1946 7 Claims. (Cl. 260-413) The present invention relates to the manufac ture of soap and particularly to the extraction of glycerine from soap produced by the saponification of fats and oils.

In the manufacture of soap, the fats which are to be converted into soap are boiled, usually by means of live steam, with caustic soda in vessels generally known as soap kettles. The products of this saponification reaction are soap, glycerine and an aqueous liquor and usually appear in the form of a homogeneous mixture. When the reaction is complete, it is customary to add a quantity of concentrated brine or solid salt to separate the soap, in the form of a curd, from the residual liquor hereinafter referred to a.s1y.e. The boiling is then stopped to allow the soap curd graduallyto rise to the top, and the lye to settle to the bottom of the soap kettle. After a period of settling, the lye, containing part of the glycerine, salt and impurities, is withdrawn from the bottom of the kettle to be specially treated for the recovery of its glycerine. The soap curd remaining in the kettle is subjected to treatments for the removal of further portions of the glycerine, salt and impurities retained within it. For this purpose the soap curd is boiled, by means of live steam, with a quantity of water to form a thick homogeneous liquid-an operation called closing the soap-and the soap is then brought into the open condition again by the addition of brine or salt. The soap curd is again allowed to rise to the top, and the lye to settle to the bottom, of the kettle; whereupon the lye is again withdrawn from the kettle.

In this operation, or washing treatment, there occurs a distribution or partition of the glycerine between the layer of soap curd and the layer of lye in such a way that the concentration of.

glycerine in the soap curd is lower than that in the lye. The proportion of glycerine removed from the kettle depends upon the proportion of the lyes to separate from it to a substantial extent. Thus the overall time required to com plete successive washing treatments may amount to several days.

The above-described procedure, and thevari ous modifications thereof which are in general use, are cumbersome, discontinuous, and produce lyes comparatively low in glycerine concentration. A further disadvantage of this process of soap washing is the lengthy overall time required for its completion. This results in a relatively high loss of radiated heat and a comparatively low output from the equipment in. a given period. The term zone is intended to mean a part 2 or the whole of the space within a vessel designed or adapted for the respective functions of agitation or settling, Such zones may be located in-' dividually, i. e., one in each of a succession of connected vessels or they may occupy contiguous spaces of a single vessel so that two or more may be contained in such a vessel. 'j A primary object of the present invention is to provide a continuous method of washing soap to extract glycerine substantially completely therefrom. Another object of the invention is to provide I a continuous method of washing soap thatrequires considerably less time than is required by conventional methods. A further object is to provide a method, of washing soap whereby the recovery of glycerine is facilitated by obtaining a lye of higher glycer ine concentration without impairing the efliciency of the soap washing and without reducing the yield of soap. These and other objects will become apparent from the disclosure of the invention.

The present invention provides for a con: tinuous stream of soap to be intimately mixed and agitated with a continuous stream of lye in a vessel or part of a vessel so that the lye will extract glycerine from, and thereby wash, the soap. The mixture of lye and soap then passes from this zone of agitation to a quiescent zone, which may be in the same vessel as the zone of agitation, or in a different vessel, and here the soap and lye are allowed to separate .by the settling action of gravity into an upper layer'of washed or partially washed soap and .a lower layer of lye. The washed soap and the settled lye are continuously removed from this zone.

In the. quiescent zone it will be apparent. that as mixed soap and lye are being continuously introduced, and separated soap and lye continuously withdrawn, it will be necessary to provide for a sufiicient space-time factor within this zone to permit adequate settling of lye from soap to take place so that no undesirable quantity of occluded lye is carried with the outflow of soap. Such a space-time factor is provided by the arrangement of the quiescent zone and its inlet and out lets, as will be hereinafter explained.

According to the present inventionQtherefor,

there is provided a continuous method of wash.,

ing soap which comprises arranging within the capacity of a single vessel or two separate vessels a pair of zones, namely a first zone suitably equipped to mix and agitate soap and lye, and a second zone of substantially quiescent flow to permit gravity settling of the soap and lye, passing continuous streams of soap and lye successive 1y into and through said first and second zones.

causing the necessary degrees of agitation and quiescence within the respective zones in order,

that the lye may extract glycerine and subsequently be settled out from the soap, continuousg 1y withdrawing the washed and settled soap from the second zone, and continuously withdrawing lye containing glycerine washed out from the soap.

The invention is preferably carried out by using several pairs of such zones in series through which the soap flows successively, the soap being washed and settled once in each pair of zones. The lye may travel generally in an opposite direction to the flow of soap, that is, it may flow from one pair of zones to the next pair in general countercurrent to the flow of soap from pair to pair of zones, although in any one pair it will flow with the soap. Alternatively, it may be divided into a number of separate parallel streams, each of which may pass through a pair of zones of agitation and settling in the same direction as the stream of soap and then be withdrawn from the process. In these ways provision may be made for either concurrent or countercurrent washing, or a combination of both these washing methods may be employed.

It will be evident from this specification that the present process dispenses with the preliminary operation of closing the soap that is usual in the prior art procedure.

The degree of recovery of glycerine is generally determined by the relative volume rates of flow of soap and lye through the system. For optimum recovery of glycerine, the speeds of movement of the soap and lye should be carefully controlled so that, when they are in admixture. the two liquids are present in the optimum proportions as established by experiment and theory. This is preferably done by insuring that the levels of the soap and the lye layers formed as a result of the settling of the lye from the soap remain substantially constant throughout the operation of the process. The level of the soap layer may be controlled by allowing the top of the soap layer to flow over a weir into a collecting pipe whence it is passed on to the next stage of operation. The level of the interface between the soap and the lye layers may be controlled by the provision of any suitable float gauge weighted to float at the interface and connected sothat its position may be indicated to an operator. It is preferable to maintain the volume ratio of the layers of soap and lye approximately the same as the ratio of volume rates of flow of soap and lye through the system.

A preferable method of extracting glycerine from soap according to the invention is by means of .countercurrent washing in which lye generally flows in the opposite direction to the soap .so that the fresh lye meets the soap weakest in glycerine and the lye already containing appreciable amounts of glycerine comes into contact with the soap containing the highest concentration of glycerine.

A particular application of the present invention is a continuous method of countercurrent washing which comprises supplying a washing vessel with an upper layer of soap curd and a lower layer of lye, injecting soap to be washed into the lower layer of lye and allowing it to rise through the lye to the top, injecting the washing lye into the upper layer of .soap curd and allowing it to fall through the soap curd to the bottom of the vessel, withdrawing the washed soap from the layer of soap curd and withdrawing lye from the layer of lye. This method may be suitably employed in two or more stages in which the lye withdrawn from a later stage is injected into the soap curd layer of an earlier stage, and the soap withdrawn from an earlier stage is injected into the lye of a later stage. In this arrangement of the process, which is only one particular application of the present invention, each washing vessel has four zones comprising two alternate zones each of agitation and settling. There is a zone of agitation at the bottom and at the top of the vessel with a zone of settling between them through which the soap rises from the former to the latter, and there is a second zone of settling through which the soap flows from the upper zone of agitation to the point at which it is withdrawn from the vessel.

Adequate space-time factors must be provided for both these zones of settling by adjusting the rates of flow proportionately to the space available within the vessels. In the first mentioned zone of settling the upward flow undergoes a limited expansion outwards with a reduction in speed, and thus time and facility are given for the lye to settle fro-m the rising soap. In the secondzone of settling the soap travels outwards in a thin surface stratum of diminishing depth from which the lye is again permitted time and facility to settle before the soap reaches the weir. The flows of the soap and of the lye are motivated along their respective directions by gravity and the force of injection.

The containing vesselfor the operations of this particular method may be the usual type of square or round soap kettle. The weir provided for the overflow of washed soap may be arranged along some portion of the vessels upper, inside perimeter, but it is preferable that it should extend around the whole of that perimeter. The injection of the soap is suitably effected at the lowest point of the pyramidially or conically shaped bottom of the .kettle, but it may be effected at other points. .It may, for instance, be situated at a remote point along the soap feed pipe. The lye withdrawal is also suitably effected at some point on the bottom of the kettle, remote from the point where the soap is injected.

For injecting the soap into the bottom of the lye layer, which washes the soap as it rises therethrough, a steam injector is preferably used. Such an injector may be of any well known type in which a jet of steam can be used to mix with and expel a liquid fed thereto. The injector should be designed to suit the several purposes of effecting a desired rate of soap curd injection, of promoting a desired degree of agitation within the vessel, and of insuring that the flow of soap rises to the top of the upper layer of the soap curd substantially within a prescribed comparatively narrow central region for reasons which will be explained hereinafter.

The lye is also preferably injected into the layer of soap by means of a steam injector. This also may be of any well known type, but having a steam jet of such diameter as to promote particular requirements regarding temperature or rate of lye flow. The actual external nozzles or diffusers of the injector may be of a fish tail pattern or of other design such as slit pipes or sprays. These injectors are preferably so arranged that their outlet nozzles are situated a few inches under the surface of the soap layer and the lye is preferably injected at .a downward angle on to suitably positioned baflle plates which. serve to deflect it upwards. The lye is thus mixed into the upper soap layer flowing over the baffles: and the mixture passes outwards towards the weir. The injectors are positioned at such a distance from the weir that substantially all thelye drops out of the upper soap layer before the soap flows over the weir. They are disposedin sufficient numbers to encompass the entire flow of outgoing soap and around the periphery of the area within which rises the soap from the lower injector, so that the soap as it is displaced from the surface by the uprising current, flows over the baflie plates and becomes intimately mixed and washed by the injected lye. The lye which settles out of the upper soap layer subsequently passes down into the lower lye layer.

The steam supplied by the soap and lye injectors keeps the soap at the desired temperature and renders unnecessary the heating of the two layers by means of live steam as in the usual soap boiling practice, which would be very undesirable for the present process as it would excessively disturb the layers and the flow of liquids through them. It is essential that the agitation of the soap and the lyes, caused by the steam within the vessel, be so localized that time and space are allowed for the lyes to settle substantially from the soap before either component reaches its succeeding stage of the process. This feature is of especial importance in the application of the process to countercurrent washing in which the flow of soap is given a washing treatment at the bottom of the vessel, substantially drained of lye during its passage upwards to the surface, again washed at the top of the vessel, and again substantially drained of lye before passing over the weir.

The above described and further embodiments of the invention will now be described with reference to the accompanying drawings in which:

Figure 1 is a diagrammatic view showing the flow of soap and lye through one type of apparatus using conventional soap kettles;

Figure 2 is a diagrammatic view showing the flow of soap and lye through a modified form and arrangement of apparatus;

Figure 3 is a diagrammatic view showing the flow of soap and lye through still another form and arrangement of apparatus; and

Figure 4 is an alternative form of part of the arrangement of Figure 3.

In Figure 1 of the drawing, two adjacent soap kettles II and I2 possessing, as is usual, dished bottoms I3 and I 4 are provided at the lower apexes of the bottoms with steam injectors I5 and I6 for continuously introducing the soap into the kettles. Steam is supplied to these injectors I5 and I6 by steam supply lines I1 and I 8, respectively. Kettles II and I2, when in operation, contain upper layers A1 and A2 of soap curd and lower layers B1 and B2 of lye. Steam injector I 5 continuously passes lye from layer B2 along lines and 2] into kettle II. Steam injector 22 serves to mix and to raise to the appropriate temperature, preferably to the boiling point, water from line 23 and brine from line 24 by means of steam from line 25. It also serves to inject the heated mixture along line 26 into kettle I2.

The injection of the lye under the surfaces 21 and 28 of soap layers A1 and A2 is effected by diffuser jets 29 and 30 placed just below the surfaces of the soap layers.

These diffusers comprise perforated pipes arranged around the central area of the kettle and parallel to the edges of weirs 3| and 32, the perforations being arranged so that the lye from them is directed downwards on to horizontal baflle plates 33 and 34 which are suspended closely beneath these diffusers and from which the injected lye is deflected forcibly upwards.

. around the upper parts of the kettles.

The lye containing the extracted glycerine is withdrawn from layer B1 of kettle II by discharge pipe 35.

The soap to be washed is supplied along line 36 to injector I5. Line 31 is used to pass soap from kettle I I to injector I6 at the bottom of kettle I2. Line 38 serves to remove washed soap from kettle I2. The levels of they soap in layers A1 and A2 are kept constant by means of weirs 3I and 32 These weirs may suitably be parts of gutters 39 and 40, which may run partly or wholly around the perimeter of the kettles. The soap flows over the top edge, acting as a weir, into the gutter, the bottom of which slopes downward to the point at which discharge lines 3'! or 38 are connected.

The method of operation is as follows. To start the process, unwashed saponified soap is charged to kettle I I, where it is given a single washing treatment; but the lyes are not removed. Similarly, unwashed soap is charged to kettle I2 where it is given two or more like washing-treatments, the first lyes being removed but that from the last washing treatment being left. This is merely one method of starting the continuous countercurrent process. Other methods will be obvious. When the lye in each case has been allowed to settle, fully saponified but unwashed soap is supplied along line 36 and injected into lye layer B1 through steam injector I5 at the bottom of kettle II. A portion of the glycerine is transferred from the soap to the lye in layer B1 during its passage through the zone of agitation agitated by the steam from the injector. The soap passes into soap layer A1 to enter a settling or quiescent zone remote from the source of agitation and becomes substantially disentangled from the lye, which falls down again into layer B1.

The soap rises upwardly from the bottom in the center of the kettle through a zone of quiescence and approaches the surface 21 to form a thin, quiescent surface stratum within the area circumscribed by diffusers 29 and then flows horizontally over bafiie plate 33 and diffusers 29, thus passing through an annular zone of agitation with lye, which removes a further portion of the glycerine. The mixture then passes outwardly along surface 21 into an annular zone of quiescence where the lye settles out of the soap before the latter flows over weir 3| into gutter 39, whence it is conveyed via line 31 to injector I6 of kettle I2. The flow of the soap from the surface stratum of layer A1 over weir 3| is regulated by the rates of feed of soap through line 36, and of lye from layer B2 through injector I9, and the rate of withdrawal of lye from layer B1 by way of line 35.

A cycle of operations takes place in kettle I2 similar to that in kettle I I. In this case fresh weak brine of the appropriate concentration and temperature is obtained by mixing water and saturated brine from lines 23 and 24 with steam in injector 22. Lyes of low glycerine concentration from other soap boiling operations may be employed at this stage. The steam injector forces the weak brine through diffusers 30 to eifect the last washing of the soap in layer A2. By adjustment of the respective rates of transfer of lye and soap curd, the appropriate quantity of washed soap flows over weir 32 into gutter 40 to the discharge line 38. A quantity of caustic soda or half spent lyes, that is. lyes containing caustic soda, may be passed into kettle I2 through injector 22 in order to provide a strong change should this be so desired.

A by-pass line 4I provided with any suitable device, such as a valve or orifice, to control the rate of flow therein, and feeding into gutter 39, may be. provided to return a portion of the lye flow from layer B2 to kettle l2 along with the soap from layer A1. This by-pass line 4! may serve several purposes, e. g., of regulating the rate of transfer of lyes from kettle l2 to kettle ll, of lubricating the passage of the soap curd down line 5. 1,, and of providing a further period of contact between the soap from layer A1 and lyes from layer B2.

It will be appreciated that, depending upon the degree of washing required, the number of units, represented in this case by kettles H and i2, can also be only one or more than two. Some latitude in the degree or" washing can be obtained for a given number of units, merely by appropriately altering the relative input rates of soapand fresh weak brine into the system.

One way of controlling the speeds of flow of the soap and lye is by varying the steam pressure applied to the jets. Preferably, however, steam at constant pressure is used, and by initial trial the orifices through which the liquids floware adjusted to give the desired rates of flow for that steam pressure. The dimensions and other particular features of the inter-connecting pipes and injectors between the vessels must be of such design that they are abl to pass rather more than the maximum flows of soap and fresh weak brine which it may be desired to charge into the system. These flows may be remotely controlled and adjusted by means of suitable electrical devices, designed to regulate the relative rates of flow of liquids, by means of which the washing treatments are maintained at a more constant degree of accuracy and; efiiciency than is possible with the standard batch procedure which, as is Well known, is greatly dependent on the skill of the operator.

Movement of soap and lye can be effected or aided by means of pumps instead of steam injectors or by a combination of pumps and injectors. Also other means of introducing heat into the system may be adopted without materially altering the above described treatments within the washing vessels. It will be seen from the above description that the arrangements are such that two washing treatments, together with the requisite and subsequent settling of the lyes, occur simultaneously in the dilferent parts of each of the washing vessels. These arrangements result in a reduction of the time required to extract the desired quantity of glycerine from th soap with a proportionate reduction in the heat lost by radiation. These factors make for a corresponding reduction in the costs of soap manufacture.

Compared with the custom of the prior art in which steam issuing from comparatively large open steam coils is employed for the purpose of boiling separate soap batches, the steam is used in a much more efiicient manner in the present process because it is employed for the several purposes of mixing and boiling the injected liquids, transferring liquids from one stage to another, and. locally agitating the contents of. the kettles. By these means the steam is so used. that substantially all its dynamic energy is absorbed in a useful manner and substantially all its total heat is required only to neutralize the radiation losses of the process which, as has been shown above, are reduced in comparison with those of the prior art processes. A further economy, particularly in steam consumption, may be effected by the present process in that a process only.

greatly increased concentration of glycerine may be obtained in the lyes produced as compared with that obtained by the usual methods. This increase may amount to as much as two or three times the concentration of glycerine in the lye for a given yield of glycerine from the soap.

The results which may be obtained from the present invention are indicated by the following general example.

In two soap kettles of approximately tons water capacity, a continuous flow of 2 to 10 tons per hour of soap can be given washing treatments as described above. A countercurrent flow of lye at a rate of approximately half that of the flow of soap is capable of extracting approximately of the total glycerine initially present in the soap. Assuming that the original fat charge, from which the soap was made, contained 9% of glycerine, then the concentration of glycerine obtainable in the lyes finally withdrawn from the present process would be approximately l0%. With a countercurrent washing treatment carried out in three pans arranged in series in the same manner, approximately of the glycerine present would be extracted, giving lyes containing approximately 11% of glycerine. These figures, quoted in these examples, are based on the premise that the fresh brine used in the present process contains little or no glycerine, and refer to results of the washing "it will be understood that. if the washed soap curd is subsequently fitted and settled, and the weak lyes therefrom are returned into the washing process, then the overall yield oi glycerine for the whole soap making procedure,

and also the final concentration of glycerine in.

the lyes, may be higher than are indicated in the given example. The usual discontinuous washing process would have resulted in a lye containing approximately one half the concentration of glycerine for the same yield of extracted glycerine from the soap. It can also be deduced from the data given in the example that the output of fully washed soap per twenty-four hours may amount to 240 tons. This, as will be obvious to those acquainted with standard procedure, is a very much larger output than could be obtainedfrom the same soap kettle capacity and employ-- ing the most efficient arrangement of the usual washing process yielding the same total of glycerine extracted.

It has been found that besides being particularly efiicient in removing glycerine from soap, the method of the invention is also efiicient in removing dirt and impurities generally present in the original mixture obtained by saponification or other soap making process.

Variations of the particular arrangement de: scribed above are possible. For example any suitable means other than that described may be used for injecting lye into the upper layers A1 and. A2 of soap. Alternatively the lye may be introduced directly into the lower lye layers B1 and B2 thus eliminating the surface washing treatment of the previously described arrangement. In such a case each vessel would have two zones only, one of agitation and one of settling.

The saponification process preceding the washing of the soap in accordance with the invention may be carried out in any suitable manner. It may with great advantage be used with a continuous saponification method, for example that described in my co-pending application No. 7 22,7 94 filed January 18, 1947. Alternatively two kettles maybe provided in which saponiflcation effected in the usual way, the saponifying operations being carried out in the kettles in succession, so that while the soap from one kettle is being injected into the lyes of the first washin kettle, a fresh charge of soap is being saponified ready to be washed when the first saponification kettle has been emptied.

The washed soap produced by the invention may be collected in vessels, such as soap kettles, in order to be fitted, settled and cleaned according to the customary batch procedure as usually practised. The invention may be usefully employed to provide a continuous supply of washed soap curd, at a constant rate, to any continuous method for the fitting or other operation necessary to complete the manufacture of the soap.

An alternative continuous countercurrent ar- I rangement of the process is shown in Figure 2. In this arrangement there are two large vessels 58 and 5| and two smaller vessels 53 and 54. The

larger vessels have overflow troughs 55 and 56 level of the soap-lye interface therein. During operation, these vessels carry soap curd layers A3 and A4 and lye layers B3 and B4, the proportions'and controls of which are similar to those indicated in the description of Figure 1. The smaller vessels 53 and 54 may be termed agitation tubes and they need consist only of suitable lengths of enlarged pipes provided with baiiles. They may, of' course, take any other appropriate form. They. are fitted with the inlet lines 63' and 64 through which the mixture of the soap and lye is injected by steam injectors 65 and 66, respectively. The turbulent passage of the mixture through the bafiied tubes causes the lye to extract glycerine from'the soap before the mixture passes out into lines 51 and 58 for settling in the lower portion of larger vessels' 58 and 5|. The soap which overflows into troughs 55 and 56 is withdrawn to the next succeeding stage of the process along lines 61 and 68. Steam injectors 69and I8 serve to pass lye to the v.next preceding stage of the process via lines II and 12, respectively. Fresh soap to be washed is introduced to the system from line 13 into small sump tank I5. The fresh lye for washing is injected into vessel 5| along line 16 by steam injector 11 which is fed by the brine, steam and water lines I8, I9 and 88, respectively. Steam from source 8| supplies injectors 65 and 69 by way of lines 82 and 83, respectively, and steam from source 84 supplies injectors 66 and I8 byway of lines 85 and 86, respectively.

Initially the equipment is charged with soap and lyes in'the manner described in connection with Figure 1. During operation the movements of soap and lye are as follows: Fresh soap to be washed flowing through line 13 into sump tank I5 meets lye from layer B3 which, withdrawn along line 59, is injected upwards by injector 69 into line The mixture then passes down line 81 to injector 65 whence it is injected through line 63 into baffled agitation tube 53 where the extraction of glycerine is completed before pass-,

ingout through'line 51 into the settling zone in the lower part of vessel 58. Here the lye settles down -to layer B: and the soap curd rises to layer- 10 A3, in the upper portion of which it passes through a central zone of agitation with lye withdrawn from layer B; through line 6| and injected into soap layer A3 by means of injector 18, line 12 and diffuser 29. Flowing outwards from this central zone, the soap passes into an annular zone of settling where the lye settles downwardly in vessel 58 and ultimately into layer B3. The space-time factor provided by conditions of flow through the vessel 58 is such that a substantially settled soap passes over weir 98 forming trough 55. A by-pass line 92 from line. I2 conveys a subsidiary flow of lye from the layer B4 into trough whence it passes, in admixture with the overflowing soap, down line 61 to steam injector 66 to be injected through line 64 into agitation tube 54. In the event the conditions of operation are such that no addition of lye to trough 56 by means of by-pass line 92 is required, line SZ-maybe closed by means of a suitable valve (not shown). In agitation tube 54, glycerine is again extracted from the soap and the mixture is ejected along line 58 into the settling zone in the lower portion of vessel 5|. The procedure within vessel 5| is similar to that in vessel 58 with the exception that diffuser 38 introduces fresh lye injected along line I6 by the injector II. The washed soap flowing over Weir 6| into trough 56 is withdrawn from the process along line 68. The lye from layer B3 is withdrawn through line 68 for glycerineextraction.

From the foregoing, it will be seen that the movements of soap and lyes are continuous, are in general countercurrent to each other, and are 1 motivated by gravity and by injection. It will further be seen that, within each pair of smaller and larger vessels, two washing treatments each comprising an agitation and a settling are given. One or more such pairs may be provided in this arrangement of the process.

The arrangement of Figure 2 is substantially similar to that shown in Figure 1, with the difference that one series of zones of agitation is accommodated in separate small vessels 53 and 54, leaving two zones of settling and one zone of agitation accommodated in each of the larger vessels 58 and 5|. A further difference between the two arrangements is that in the arrangement of Figure 2, the larger vessels are so designed as to give the contiguous zones within them dimensional shapes approximately more suited to their particular functions and Without the superfluous volumes usually unavoidable when, as shown in Figure 1, ordinary types of soap kettles are adapted for the process. The overall effect of these differences is to reduce the stock of 'material in process with a consequent saving in radiated heat losses and an increase of output calculated on a time-capacity basis.

A further continuous countercurrent arrangement of the process is shown in Figure 3 of the accompanying drawing, in which the zones of agitation and settling reside singly in separate and specially equipped vessels.

In Figure 3 there is shown a series of baffled tubes I88, NH and I82 designed for the sole purpose of agitating mixtures of soap curd and lye bottomed settling trays i It, H and Ht, fitted with centrally placed funnels H7, H3 and H9 which are connected with lines IIll, III and H2, respectively, so that the agitated mixture of soap and lye may be introduced centrally into the trays for the purpose of settling. Flowing from the-mouths of the funnels H7, H3 and H9, these mixtures gradually separate into the respective upper-layers A5, A andAf'z, of soap and lower layers Be, Be and B of lye. Any suitable gauges to indicate the approximate level of the interface between the two layers may be provided for trays H4, I I5! and II'G. The trays are fitted around tlieir'inside perimeters with troughs I23, I21! 5113122, into which the soap flows over weirs 23,124 and 'l25 tobe carried away by withdrawal lines I26, I27 I28 respectively, to the next succeeding stage of the process. Lines E29, I35 and ISI serve to withdraw lyes from the respective layers B5, B6 and 1331 The lye from the layer B5 is withdrawn from the process to be worked up for the recovery of glycerine, but the lyes from layers B6 and B7 are fed to steam injectors I33 and I3 3, respectively, which are supplied from a source of steam I35 by steam lines I35 and I3? in order that they may be injected upwards into the next preceding stage of the process.

The soap to be washed is introduced into the process through line I lii and a small sump tank I4I. The fully washedsoap is finally withdrawn along line i28. The fresh brine or lye used for the washing is introduced by steam jet Hi2 fed by the brine, steam and water lines I43, I44 and 545, respectively.

The method of procedure will be more readily understood if it is first described on the assumption that it is already in operation, that is to say, each tray has its'res pective upper layer of soap and its lower layer of lye already established. In this case the soap to be washed enters sump tank I4I through line I55 and there mixes with lye withdrawn through line I35! from layer 1360f tray H5 and injected upwards by steam injector I33 along line'l iii. The mixture of soap and lye then passes through line It? into steam injector Ills which injectsit along line I513 into agitation tube 169' and thence out through line II?! into funnel II! of settling tray H4 where -the soap and lye settleinto the layers A5 and B5, respectively. The lye is withdrawn from layer B5 to pass; out of the system by line I29 and, the soap fio'ws over weir I23 into trough 128 where it meets lye withdrawn from layer B7 in tray I it through line I3I and which has been injected upwards by steam injector I34 through line I48. This further mixture of soap and lye is injected into agitation tube IOI through line I26, steam injector I01 and line Ill l, whence it is transferred to settling tray H5 through line HI and through funnel H8. The lye again settles out and is withdrawn through line I36 to be injected upwards as mentioned above. The soap flowing over weir I24 into trough I2I is mixed with fresh lye introduced through line I50 from the injector arrangement at I 12. The mixture of soap and lye in trough I2I is withdrawn through line I2? and injected into agitation tube I02 through line I05 by steam injector I08. From there it is transferred to settling tray I I6 through line H2 and funnel H9. Here again the lye settles out, this time into the layer B1 from which 12 it is withdrawn through line I3I to be injected upwards as mentioned above. I

The soap which passes into the upper layer Aw then flows over weir I25 into trough I22 to be withdrawn through line I28.

It will'be seen from the above description that there are a series of stages of alternate agitation and settling, the soap generally passing continuously downwards through the System by gravity whilst the lye generally passes continuously upwards in a countercurrent direction and is moved by injection. If desired, the movements of soap and lye may be in the opposite directions to those shown, so that the soap passes upwards by injection while the lye moves downwards by gravity. The whole process can be controlled by regulation of the flow materials, if desired, in co-operation with any means, such as the aforementioned gauges for indicating the level of the interfaees, 1

In this arrangement of the process the spacetime factor provided in the settling zones is similar to those provided ior the upper settling zones of the two previously described arrangements, the soap travelling outwards in a thin surface stratum of diminishing depth from which the lye is permitted time facility to settle before the soap reaches theweir. The rates of flow are proportionate to the mean depth of the surface layer and to the diameter, or length, of the settling trays. Any other suitable designs of agitation chambers and settling trays may be employed. For example, in the case where pumps are used to move the liquids, the pump chambers themselves may serve as the agitation chambers, care being talgen that the liquid remains agitated for a suificient length of time for a satisfactory extraction of glycerine to be obtained. The system may be operated in one or any number of stages. The various vessels and trays of the apparatus maybe disposed in any vertical, lateral or other arrangement which may be found suitable or desirable, and may be combined. in complete units to suit convenience of manufacture or installation.

This particular arrangement of the process also provides a means whereby a quality, or run of soap can be completely withdrawn from the equipment and yet the respective lyes may be left behind in readiness to treat another quality, or run of soap. FOl bhlS purpose the troughs in the settling trays are fitted on their inner sides with small sluice gates l5I, I52 and I 53, the function of which will be explained below.

When the flow of fresh, unwashed soap down line I40 ceases, the withdrawal of lye from layer B5 is stopped by closing valve I5 Similarly, the withdrawal of lye from layer 136 through line I30 is stopped by closing valve I55 and the operation of injector I06 is stopped by closing valve I56. Any suitable sluice gate, such as sluice gate I5I shown diagrammatically in the drawing, is gradually opened to drain off the soap layer A5. When this operation is completed, theupward injection of lye from layer B7 by means ofsteam injector I34'is stopped by closing valves I57 and I66 and the introduction of soap-lye mixture from trough I29 into agitator tube ml by means of steam injector IE4 is stopped by closing valve I58. In the meantime, however, thesoap drained from the whole ofsoap layer A5, accompaniedby the appropriate quantity of injectedv lye from the layer B7, passes with agitation into the settling tray H5, from which, it will be remembered, no lye islnow being withdrawn, The result of this move;

13 ment is that the lye layer Be increases in bulk and displaces soap from the layer A6- Sluice gate I52 is now adjusted to complete the draining of soap layer As, after which the steam feed to injectors I06 and I42 is stopped by closing valves I59 and I66. While soap laywer As is being drained, the admission of fresh lye into the trough I2! is continued, the mixture of thetwo being agitated in agitator I62 and being conducted into settling tray I I 6. Since in the meantime the withdrawal of lye from layer B7 has been stopped, the consequence of this last movement of soap and lye into tray H6 is that lye layer B7 increases in depth and displaces the soap layer A7. Sluice gate I53 is then opened to complete the draining of this soap layer A7 and a further small quantity of fresh lye is injected to complete this draining. When this operation is complete, all sluice gates are closed and steam is shut oif completely. It must be noted that the draining of an upper layer of soap must be conducted gradually so that the consequent dis placement of the next lower soap layer does not become too rapid for the respective flow of lye by which it is to be washed.

It will thus be seen that in this manner all soap layers are substantially withdrawn from the equipment and that the soap in each soap layer in turn undergoes the remaining stages of its washing treatment. Further it will be seen that all settling trays, except the first one, are left with an increased bulk of lye. In this condition the equipment is ready to recommence the washing treatments of another quality, or run, of soap. In the special case of originally starting the equipment for its first washing treatment of soap, this condition with respect to the lye layers can obviously be fulfilled by charging the settling trays with lye layers of requisite bulk and, if desired, glycerine concentration.

The lyes whichhave been left behind by a preceding quality of soap need not necessarily possess a concentration of electrolyte which is suitable for a succeeding quality. Hence an adjustment of this electrolyte concentration may be required before recommencing the process. For this purpose the requisite quantity of either strong brine from line I43 or water from line I45 is injected by steam injector I 32 by way of line I56 into line I6! from which it is conveyed through lines I29, I36 and I3I, into lye layers B5, B6 and B7 respectively. In this operation, valves I66, I62, I63, and I64 are open, valves I54, I65, I55 and I57 are closed, and the direction of flow in lines I29, I36 and I31 is opposite to that indicated by the arrows.

The process is now restarted by closing valves I62, I63 and I64, feeding the new fresh soap down line I46 into sump tank MI and opening valves I55 and I65 for injector I33 in order to bring up lye from the layer B6 to mix with the new soap. Steam for injector I66 is now turned on by opening valve I56 to inject the new mixture of soap curd and lye through the agitation tube I60, and so convey it to settling tray II4. The withdrawal of lye from layer B through line I29 is begun again by opening valve I54. Eventually the soap layer A5 is replaced and begins to overflow into the trough I26, whereupon the upward injection of lye from layer B7 by injector I3 1 is once more put in operation by opening valves I51 and I66. It will be noticed that by this time the lye layer Be'will have been reduced substantially to its normal level and so space is \nowavailable in settling tray I I5 to accom:

'14 modate "the new .fiow ofmixture of soap and lye whichis injected intov it along the familiar route. Again the soap layer As is replaced and commences to flow over weir I24 into trough I2I and again the injected flow of fresh brine along line I56 is set in motion, the resultant mixture of soap and lye being injected to settling tray I I6 by the already describedroute. Meanwhile the lye layer B7 has been'reduced substantially to its normal level and space is thus provided in settling tray I I6 for a new soap layer Av, which after a time flows over weir I25 into trough I22 to be carried away down line I28. In this manner the process is completely restarted and functions again in all its parts for the purpose of the continuous countercurrent washing of a further quality of soap. It will have been appreciated from the above description that the series of operations necessary for this restarting takes place in the reverse order to the series of operations required to withdraw soap and stop the process.

The great advantage of this arrangement of the process is that it carries only a comparatively low stock of soap in its equipment and is thus especially applicable for the production of smaller quantities of various soap qualities.

In all embodiments of the invention, it is found desirable that the zone of settling should present a fairly high degree of symmetry, particularly in those cases where the settled soap flows over a weir, that is to say in the cases of the upper settling zones in vessels II and I2 of Figure 1 and 50 and 5| of Figure 2 and of trays H4, H5 and H6 of Figure 3. In these cases the arrangement should be such that the time taken for the soap t flow from the point of injection into the settling zone to the point of leaving the zone at the weir should be the same for all paths along which a given small mass of soap may fiow. This ensures that the degree ofsettling' is uniform for all parts of the soap mass leaving the zone. If this symmetry is not achieved, the soap flowing over the weir may have different physical characteristics at different points along the length of the latter, giving rise to'an unhomogeneous product leaving the zone. In an extreme case stagnant pockets or areas of soap may form, causing a reduction in effective settling space and loss of operative efficiency.

' To achieve this symmetry, the lye injected into the soap layer in the arrangements of Figures 1 and 2 should'be directed to flow towards the whole length of the weirs 3|, 32, 90 and 9|. If the vessels are circular in shape, a single injector may spread a disc-shaped layer of lye into the soap. If the vessels are rectangular in shape with the weir arranged round all four sides, a correspondingly rectangular bank of injectors placed in the central area of the pan is provided. Similar cons'iderations apply to the position of the weirs and the manner of introducing the mixture of soap and lye into settling trays II4, IE5 and H6 of Figure 3.

However, in the case of an arrangement such as is shown in Figure 3 where the zone of settling is in a separate vessel not at the same time containing a zone of agitation, greater freedom exists in the design of the vessel to promote the desired objects of 'sym metryof flow. In Figure 4 is shown an alternative arrangement of a settling tray I I4 in which the soap/lye mixture from the agitation vessel I00 is passed through pipe I I0 into a slotted distribution pipe I I9 lying across the width of the tray at thebottom of an end trough eamed It .sebmereedeb ffle p a e 1 Ha. he

soap/lye mixture passes over the top of this baffle Illa and thence across the tray to the overflow weir I23 for the settled soap, which flows down pipe I26 and thence to the next stage of the process. The flow of the soap across the tray, during which lye settles out into layer B is thus symmetrical lengthwise of the tray, instead of radially as in Figure 3. The remaining trays I I5 and l [6 may be arranged in a similar manner to that shown in Figure 4.

The flow of lye may follow paths other than those shown in the above described arrangements of the process. For example in Figure 3, instead of the lye flowing in general countercurrent to the flow of soap, fresh brine from the pipe I53 may be fed to each of the troughs I20 and I2! and to sump iii and the lye withdrawn from the trays H 3 and H5 may join that from tray I Hi and leave the process. In this case fresh brine is used t wash the soap at each stage. Alternatively, four settling trays with four agitation tubes may be provided. The soap passes through all four in succession, and fresh brine is fed to the second and fourth washing stages, and is returned to the first and third washing stages respectively. Which of these various ways of moving the lye through the washing stages is preferable will depend upon the efficiency of glycerine extraction, and the concentration of glycerine in the recovered lye which it is desired to attain.

It is thought that this invention and its numerous advantages will be understood from the foregoing description. It is obvious that various changes can be made in the arrangement, form, construction and type of the various elements and that various modifications can be made in the process without departing from the spirit or scope of the invention. All such modifications and changes are intended to be included within the scope of this invention.

I claim:

1. A continuous method of washing soap for extracting glycerine therefrom in the absence of centrifuging which comprises continuously mixing, in a zone of agitation, a continuous stream of glycerine-containing soap with a continuous stream of lye, thereby continuously washing the soap in said soap stream with the lye in said stream of lye to transfer the glycerine' fromthe soap to the lye and forming a combined stream of washed soap and glycerine-enriched lye; continuously passing said combined stream from said zone of agitation into a settling zone within a vessel filled with soap and lye separated into an upper layer of soap and a lower layer of lye, said combined stream of washed soap and glycerineenriched lye being introduced into said settling zone below the surface of the layer of soap in the vessel, the lye in said settling zone descending by the action of gravity to the layer of lye in the lower portion of the vessel and the washed soap ascending to the upper layer of soap to form a thin, quiescent surface stratum of washed soap; continuously withdrawing a thin stream of washed soap from the surface stratum in the settling zone by overflow at the top of the vessel; and continuously withdrawing glycerine-enriched lye from the layer of lye in the lower portion of the vessel; the rate of introduction of soap and lye into the settling zone and the rates of withdrawal of the washed soap and the glycerineenriched lye from the vessel being interrelated and adjusted to the space available in the vessel to avoid occlusion of lye'in the washed soap with--' i5 drawn from the surface of the settling zone and to maintain the proportion of soap to lye in the vessel substantially constant.

2. A continuous method of washing soap. for extracting glycerine therefrom in th absence of centrifuging which comprises filling a vessel having an overflow initially with soap and lye to form, by gravity settling, an upper layer of soap and a lower layer of lye; continuously introducing a stream of glycerine-containing soap into the lower portion of the vessel; continuously introducing a stream of lye into the upper portion of the vessel below the surface of the layer of soap; said continuous introductions of soap and lye forming a lower Zone of agitation localized in the lower portion of the Vessel wherein the continuously introduced stream of soap is washed with the lye in said lower layer to transfer glycerine from said stream of soap to the lye, an upper zone of agitation localized in the upper portion of the vessel and not extending to the overflow wherein the soap in the upper layer is washed by the continuously introduced stream of lye to transfer glycerine from said soap to said lye, a first settling zone intermediate the lower and upper zones of agitation wherein the glycerine-enriched lye from the upper zon of agitation descends by the action of gravity to the lye in the lower portion of the vessel and the washed soap from the lower zone of agitation ascends by displacement, and a second settling zone between the upper zone of agitation and the overflow wherein the washed soap from the upper and lower zones of agitation ascends to form a thin, quiescent surface stratum of washed soap and wherein any lye in said washed soap descends by the action of gravity to the lower zone of agitation; continuously withdrawing a shallow stream of washed soap from the surface stratum of the second settling zone by overflow at the top of the vessel; and continuously withdrawing glycerineenriched lye from the lower portion of the vessel, the rates of introduction of glycerine-containin soap and lye and the rates of withdrawal of washed soap and glycerine-enriched lye being interrelated and adjusted to the space available in the vessel to avoid occlusion of lye in the washed soap withdrawn from the surface of the second settling zone and to maintain the proportion of soap to lye in the vessel substantially constant.

3. The method defined in claim 2 wherein the rate of introduction of lye is approximately onehalf the rate of introduction of glycerine-containing soap and the combined rate of introduction of soap and lye, measured in units of weight per hour, is up to about one-eighth the capacity of the vessel, measured in the same units of weight.

4; A continuous method of washing soap for extracting glycerine therefrom in the absence of centrifuging which comprises filling a vessel having an overflow initially with soap and lye to form, by gravity settling, an upper layer of soap and a lower layer of lye; continuously mixing, in a zone of agitation outside the vessel, a continuous stream of glycerine-conta-ining soap with a continuous stream of lye, thereby continuously washing the soap in said soap stream with the continuously introducing a stream of lye into the upper portion of the vessel below the surface of the layer of soap; said continuous introductions of washed soap and lye forming a zone of agitation localized in the upper portion of the vessel and not extending to the overflow wherein the soap in the upper layer is washed by the continuously introduced stream of lye to transfer glycerine from said soap to said lye, a first settlin zone in th lower portion of the vessel wherein the glycerine-enriched lye from the upper zone of agitation descends by the action of gravity to the layer of lye in the lower portion of the vessel and the washed soap introduced with the combined stream of washed soap and lye into the lower portion of the vessel ascends by displacement, and .a second settling zone between the zone of agitation in the vessel and the overflow wherein the washed soap ascends to form a thin, quiescent surface stratum of washed soap and wherein any lye in said washed soap descends by the action of gravity to the lower portion of the vessel; continuously withdrawing a shallow stream of washed soap from the surface stratum of the second settling zone by overflow at the top of the vessel; and continuously withdrawing glycerine-enriched lye from the lye in the lower portion of the vessel, the rates of introduction of soap and lye into the vessel and the rates of withdrawal of washed soap and glycerine-enriched lye therefrom being interrelated and adjusted to the space available in the vessel to avoid occlusion of lye in the washed soap withdrawn from the surface of the second settling zone and to maintain the proportion of soap to lye in the vessel substantially constant.

5. A continuous method of washing soap for extracting glycerine therefrom in the absence of centrifuging which comprises filling a vessel initially with soap and lye to form, by gravity settling, an upper layer of soap and a lower layer of lye; continuously introducing a stream of glycerine-containing soap and a stream of lye into the lower portion of the vessel; said continuous introductions of soap and lye forming a zone of agitation localized in the lower portion of the vessel wherein the continuously introduced stream of soap is washed with the lye in said lower layer to transfer glycerine from said stream of soap to the lye and the lye in said lower layer is continuously replenished by the continuously introduced stream of lye, and a settling zone above the zone of agitation wherein the washed soap from the zone of agitation ascends to form a thin, quiescent surface stratum of washed soap and wherein any lye in said washed soap descends by the action of ravity to the zone of agitation; continuously withdrawing a shallow stream of washed soap from the surface stratum of the settling zone by overflow at the top of the vessel; and continuously withdrawing glycerine-enriched lye from the lye in the lower portion of the vessel, the rates of introduction of glycerine-containing soap and lye and the rates of withdrawal of washed soap and glycerine-enriched lye being interrelated and adjusted to the space available in the vessel to avoid occlusion of lye in the washed soap withdrawn from the surface of the settling zone and to maintain the proportion of soap to lye in the vessel substantially constant.

6. A continuous method of washing soap for extracting glycerine therefrom in the absence of centrifuging which comprises continuously mixing, in a zone of agitation, a continuous stream of glycerine-containing soap with a continuous stream of lye, thereby continuously washing the soap in said soap stream with the lye in said stream of lye to transfer the glycerine from the soap to the lye and forming a combined stream of washed soap and glycerine-enriched lye; continuously passing said combined stream from said zone of agitation into the center of a shallow vessel having a sloping bottom to form a settling zone within the vessel wherein the lye in said continuous combined stream descends by the action of gravity to form a layer of glycerine-enriched lye in the lower portion of the vessel and wherein the washed soap ascends to form a thin, quiescent surface layer of washed soap diminishing in depth as it moves toward the edge at the top of the vessel; continuously withdrawing a shallow stream of washed soap from the surface layer of the settling zone by overflow at the top edge of the vessel; and continuously withdrawing glycerine-enriched lye from the lower portion of the vessel, the rates of introduction of soap and lye into the vessel and the rates of withdrawal of washed soap and glycerine-enriched lye therefrom being interrelated and adjusted to the space available in the vessel to avoid occlusion of lye in the washed soap withdrawn from the surface of the settling zone and to maintain the proportion of soap to lye in the vessel substantially constant.

'7. A continuous method of washing soap for extracting glycerine therefrom in the absence of centrifuging which comprises continuously mixing, in a zone of agitation, a continuous stream of glycerine-containing soap with a continuous stream of lye, thereby continuously Washing the soap in said soap stream with the lye in said stream of lye to transfer the glycerine from the soap to the lye and forming a combined stream of washed soap and glycerine-enriched lye; continuously passing said combined stream from said zone of agitation into a shallow, elongated vessel at one end thereof, said vessel having a sloping bottom, to form a settling zone within the vessel wherein the lye in said continuous combined stream descends by the action of gravity to form a layer of glycerine-enriched lye in the lower portion of the vessel and wherein the washed soap ascends to form a thin, quiescent surface layer of washed soap diminishing in depth as it moves toward the other end of the vessel; continuously withdrawing a shallow stream of washed soap from the surface layer of the settling zone by overflow at said other end of the vessel; and continuously withdrawing glycerine-enriched lye from the lower portion of the vessel, the rates of introduction of soap and lye into the vessel and the rates of withdrawal of washed soap and glycerine-enriched lye therefrom being interrelated and adjusted to the space available in the vessel to avoid occlusion of lye in the washed soap withdrawn from the surface of the settling zone and to maintain the proportion of soap to lye in the vessel substantially constant.

RONALD VINCENT OWEN REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,300,749 Scott Nov. 3, 1942 2,300,750 Scott Nov. 3, 1942 2,411,468 Sender Nov. 19, 1946 2,411,469 Sender Nov, 19, 1946 

1. A CONTINUOUS METHOD OF WASHING SOAP FOR EXTRACTING GLYCERINE THEREFROM IN THE ABSENCE OF CENTRIFUGING WHICH COMPRISES CONTINUOUSLY MIXING, IN A ZONE OF AGITATION, A CONTINUOUS STREAM OF GLYCERINE-CONTAINING SOAP WITH A CONTINUOUS STREAM OF LYE, THEREBY CONTINUOUSLY WASHING THE SOAP IN SAID SOAP STREAM WITH THE LYE IN SAID STREAM OF LYE TO TRANSFER THE GLYCERINE FROM THE SOAP TO THE LYE AND FORMING A COMBINED STREAM OF WASHED SOAP AND GLYCERINE-ENRICHED LYE; CONTINUOUSLY PASSING SAID COMBINED STREAM FROM SAID ZONE OF AGITATION INTO A SETTLING ZONE WITHIN A VESSEL FILLED WITH SOAP AND LYE SEPARATED INTO AN UPPER LAYER OF SOAP AND A LOWER LAYER OF LYE, SAID COMBINED STREAM OF WASHED SOAP AND GLYCERINEENRICHED LYE BEING INTRODUCED INTO SAID SETTING ZONE BELOW THE SURFACE OF THE LAYER OF SOAP IN THE VESSEL, THE LYE IN SAID SETTING ZONE DESCENDING BY THE ACTION OF GRAVITY TO THE LAYER OF LYE IN THE LOWER PORTION OF THE VESSEL AND THE WASHED SOAP ASCENDING TO THE UPPER LAYER OF SOAP TO FORM A THIN, QUIESCENT SURFACE STRATUM OF WASHED SOAP; CONTINUOUSLY WITHDRAWING GLYCERINE-ENRICHED WASHED SOAP FROM THE SURFACE STRATUM IN THE SETTLING ZONE BY OVERFLOW AT THE TOP OF THE VESSEL; AND CONTINUOUSLY WITHDRAWING GLYCERINE-ENRICHED LYE FROM THE LAYER OF LYE IN THE LOWER PORTION OF THE VESSEL; THE RATE OF INTRODUCING OF SOAP AND LYE INTO THE SETTLING ZONE AND THE RATES OF WITHDRAWAL OF THE WASHED SOAP AND THE GLYCERINEENRICHED LYE FROM THE VESSEL BEING INTERRELATED AND ADJUSTED TO THE SPACE AVAILABLE IN THE VESSEL TO AVOID OCCLUSION OF LYE IN THE WASHED SOAP WITHDRAWN FROM THE SURFACE OF THE SETTLING ZONE AND TO MAINTAIN THE PROPORTION OF SOAP TO LYE IN THE VESSEL SUBSTANTIALLY CONSTANT. 